Rotary lug breeches safely secure a cartridge in a cartridge chamber of a muzzle and/or barrel prior to releasing a shot. To secure the base of the cartridge, a head is introduced into a bolt head and/or receiver and secured there by a rotational motion and/or interaction with a mounting socket and/or lugs. The locking lugs are radially disposed inwards of the receiver.
To retain the cartridge to be fired, breech lugs pass through and past gaps between the locking lugs in the bolt head toward the cartridge chamber. Bolt gaps are also formed that correspond to the locking lugs and/or rows of locking lugs of the bolt head through which the bolt can pass after the bolt has been inserted into the bolt head. To lock the breech, the bolt is subsequently rotated in the receiver to place the breech lugs rearwards of the locking lugs. Specifically, with the subsequent rotational motion of the bolt in the receiver, end rearward facing surfaces of the breech lugs are in front of end forward facing surfaces of the locking lugs.
With the cartridge secured, the cartridge may be fired and the resulting recoil forces directed through the impact base, the bolt, the breech and locking lugs to the receiver rigidly connected to the barrel. Directing the recoil forces through the impact base, the bolt, the breech and locking lugs to the receiver substantially prevents the breech from moving backwards in an undesired manner immediately after firing a shot.
With automatic weapons in which new ammunition is introduced via a breech configuration and/or assembly without manual reloading, the bolt is normally located in a bolt carrier. The bolt carrier is pushed forwards by a breech spring and, as a result of recoil effects, is rearwardly pushed by a propellant gas and rod (e.g., piston assembly) against the effect of a breech spring. The rotational motion for locking and releasing the bolt is obtained by a gate control (e.g., a slot). Based on movement of the bolt and/or bolt carrier, the gate control controls the relative movement and/or rotational movement of bolt and/or bolt carrier. Mauser MG 34, the MG4, and the SLB 2000 from Heckler & Koch, the assignee of the present patent, include rotatory lug breeches. Other rotary lug breeches are described in DE 196 00 459 or EP 0 188 681.
CH 51131 A1 describes a straight pull breech having locking lugs that include pitched breech surfaces that slide along corresponding locking niches on side walls. As the breech unit is released, the empty cartridge shells are also released.
DE 419803 A describes a recoil-control rotary lug breech in which rotational motion of the locking lugs are transferred to linear motion via a curved surface.
DE 196 00 459 A1 describes a rotary head breach in which the bolt has two rows of breech lugs lying in a row along the longitudinal axis. The lateral flanks of the breech lugs define a high-pitch thread along the longitudinal axis of the breech. There may be twelve lugs per row. Thus, in releasing and locking the bolt in the receiver, an interaction of the breech and locking lugs causes an additional rotational bolt motion, which locks or releases a control pin from a safety groove. The bolt is also provided with diagonal locking lugs. The safety groove runs radially or in a circumferential direction of a guide sleeve (e.g., bolt carrier).
U.S. Pat. No. 2,364,548 describes a gas-pressure operated rotary head breech in which two locking pins of the bolt and two L-shaped locking grooves and/or pockets in the receiver form a bayonet mount. The compulsory guide of the locking pins at the control surfaces enable corresponding guide surfaces in locking pockets of the receiver to have relatively high tolerances.
U.S. Pat. No. 2,775,920d describes a rotary breech head in which rotational motion of a bolt is initiated by relative motion between the bolt carrier and the bolt in the longitudinal direction. The relative motion is enabled by corresponding guide grooves and guide tracks provided with a pitch. The rotational motion is completed by inertia of the rotating bolt in the receiver. A screwing motion of the bolt is substantially prevented.
EP 0 188 681 describes using a rotary bolt having two rows of breech lugs lying behind one another in the longitudinal axis and the recoil effects of an advancing rotary lug breech toward a radial annular surface at a rear edge of the barrel to the breech lugs. The edges of the breech surfaces are rounded. As seen from the perspective of the shooter, the right-hand edge of the bolt surfaces are beveled. Beveling the bolt surfaces creates a safety clearance for the recoiling breech surfaces.
Rotary lug breeches are also used in machine guns in which the breech carries out propulsion functions including loading ammunition from a cartridge belt, removing and reliably discarding empty, fired cartridge shells and transporting the ammunition belt with cartridges relative to the firearm and/or breech. When the machine gun is cycled, substantial masses are moved back and forth in the weapon in the direction of firing and transverse to the direction of firing. The direction of firing is in the direction of the bore axis and the direction transverse to the direction of firing is in the direction of the operation of the cartridge belt feed. In cycling, the bolt rotationally moves back and forth quickly. If the firearm is fired at a higher cadence, substantial longitudinal, transversal and/or rotational accelerations occur that limit the aiming precision and cause manually loaded machine guns to stray when fired. If the firing cadence is reduced, thereby reducing the breech speed and/or acceleration, the operational forces needed to reload and feed ammunition may no longer be readily applied causing the weapon to fail.